With the miniaturized capabilities afforded by the discovery of solid state electronics, various improved means of dissipating the heat generated by solid state components have been investigated. The standard of forced convection means appears to have reached its limit of practicality in that the amount of air that is required to provided sufficient cooling for the limited heat dissipating surfaces introduces a noise problem, and without some auxiliary techniques cannot maintain each of a large number of components within its critical, narrow operating temperature range. Accordingly, especially in connection with large scale computer systems, various innovative cooling systems have been devised. One of the more recent systems investigated has been the gas encapsulated cooling module of U.S. Pat. No. 3,993,123, issued Nov. 23, 1976, wherein an encapsulated cooling unit or module is provided which utilizes inert gas having good thermal conductivity as the encapsulated medium in combination with a conductive heat transfer arrangement. The integrated circuit chips to be cooled in the system are reverse mounted and connected face down to a substrate through solder balls. Because of this type of mounting the chip is often slightly tilted. The tilt provides a poor surface contact between the conductive stud element and the back side of the chip. Accordingly, a high thermal resistance joint is formed which, in the case of the patent, required the insertion of a thermal conductive gas to lower the resistance.
U.S. Pat. No. 4,156,458, issued May 29, 1979, sets forth a heat conductive metal foil bundle of sufficient thickness to contact sufficient surface area of the exposed back side of the chip to provide the required heat transfer, and which is sufficiently thin to be flexible enough to absorb differences in distance between the chip and the heat sink due to tilt as well as to expand and contract due to temperature changes, and which is of sufficient length to connect to the heat sink at or near the other end thereof. Good heat transfer was obtained using this arrangement, however, the large thickness of the bundle often adversely effected the flexibility and, therefore, exceeded the surface force limits established by the solder ball mountings.